Etch back processes of bonding material for the manufacture of through-glass vias

ABSTRACT

A method for manufacturing vias in a glass substrate includes bonding, through a bonding layer, a first face of the glass substrate including a plurality of holes to a first face of a glass carrier. The bonding layer has a thickness t between the first face of the glass substrate and the first face of the glass carrier and extends into at least some of the plurality of holes to a depth h from the first face of the glass substrate. The method includes etching back the bonding layer to a depth d through the plurality of holes in the glass substrate. The depth d is less than the sum of the thickness t and the depth h. The method can include filling the plurality of holes with an electrically conductive material, and de-bonding the glass substrate from the bonding layer and the glass carrier.

This application is a continuation of U.S. patent application Ser. No.14/699,393 filed on Apr. 29, 2015, which claims the benefit of priorityunder 35 U.S.C. § 119 of U.S. Provisional Application Ser. No.61/986,370 filed on Apr. 30, 2014, the content of each is relied uponand incorporated herein by reference in its entirety.

BACKGROUND

1. Field

The present specification generally relates to the manufacture ofthrough glass vias and, more specifically, to etching processes used tomanufacture through glass vias.

2. Technical Background

Through-substrate vias provide electrical connections between layers ina physical electronic circuit or chip. For example, in athree-dimensional stacked integrated circuit, the through-substrate viasenable integration of electronic components both vertically andhorizontally. Conventionally, through-substrate vias employ a siliconsubstrate. However, because glass is less expensive than silicon, glasssubstrates are becoming more prevalent in electronic devices.

While a reduced cost, a flexible coefficient of thermal expansion, andthe inherent insulation properties of glass make the choice of glass asa substrate an attractive option, the use of glass presents severalchallenges. In particular, one challenge of using a glass substrate isthe handling of a suitably thin piece of glass during the manufacturingprocess. Another challenge is forming holes in a glass substrate at ahigh rate of speed without cracking the glass at the entrance holes andwithout adversely affecting metallization of the vias.

Accordingly, a need exists for alternative methods for formingthrough-glass vias which enhance manufacturability and achieve reliablemetallization of the vias.

SUMMARY

According to one embodiment, a method for manufacturing a plurality ofvias in a substrate includes bonding a first face of the substrateincluding a plurality of holes to a first face of a carrier using abonding layer. The bonding layer has a thickness t between the firstface of the substrate and the first face of the carrier and extends intoat least some of the plurality of holes to a depth h from the first faceof the glass substrate. The method also includes etching the bondinglayer to a depth d through the plurality of holes in the substrate. Thedepth d is less than the sum of the thickness t and the depth h. Themethod also includes filling the plurality of holes with a material toform the plurality of vias.

In another embodiment, a method for manufacturing a plurality of vias ina substrate includes bonding a first face of the gsubstrate including aplurality of holes to a first face of a carrier, etching the bondinglayer to a depth d through the plurality of holes in the substrate usinga wet etch process, filling the plurality of holes with an electricallyconductive material to form the plurality of vias in the substrate, andde-bonding the glass substrate including the plurality of vias from thebonding layer and the carrier. The first face of the substrate is bondedto the glass carrier through a bonding layer. The bonding layer has athickness t between the first face of the substrate and the first faceof the carrier, and the depth d is measured from the first face of thesubstrate. The depth d is less than the thickness t. The electricallyconductive material extends into the bonding layer by the depth d suchthat when the substrate is de-bonded from the bonding layer and thecarrier, the electrically conductive material protrudes from the firstface of the substrate.

In another embodiment, a method for manufacturing a plurality of vias ina substrate includes bonding a first face of the substrate including aplurality of holes to a first face of a carrier through a bonding layer,etching the bonding layer to a depth d using a dry etch process, fillingthe plurality of holes with an electrically conductive material to formthe plurality of vias in the substrate, and de-bonding the substrateincluding the plurality of vias from the bonding layer and the carrier.The bonding layer has a thickness t between the first face of thesubstrate and the first face of the carrier. The depth d is measuredfrom the first face of the substrate and is equal to the thickness t.The first face of the carrier is a stop layer for the dry etch process.When the substrate is de-bonded from the bonding layer and the carrier,the electrically conductive material forms pillars extending from thefirst face of the substrate a length l, wherein the length l is equal tothe thickness t of the bonding layer.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments described herein, including the detailed description whichfollows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a glass substrate including a plurality ofholes bonded to a glass carrier through a bonding layer in accordancewith one or more embodiments;

FIG. 2 schematically depicts a cross-section of a process of etchingback the bonding layer through the plurality of holes in the glasssubstrate depicted in FIG. 1 in accordance with one or more embodiments;

FIG. 3A schematically depicts a cross-section of a process of etchingback the bonding layer to a depth d that is equal to a height h of adistal face of the bonding layer within the plurality of holes in theglass substrate in accordance with one or more embodiments;

FIG. 3B schematically depicts a cross-section of a process of etchingback the bonding layer to a depth d that extends a length l into thebonding layer in accordance with one or more embodiments;

FIG. 3C schematically depicts a cross-section of a process of etchingback the bonding layer to a depth d that is equal to the sum of theheight h of a distal face of the bonding layer within the plurality ofholes in the glass substrate and length l into the bonding layer inaccordance with one or more embodiments;

FIG. 4A schematically depicts a cross-section of a metal filling processin which the electrically conductive material forms a plurality of viashaving a mushroom shape in accordance with one or more embodiments;

FIG. 4B schematically depicts a cross-section of a metal filling processin which the electrically conductive material forms a plurality of viashaving a pillar shape in accordance with one or more embodiments;

FIG. 4C schematically depicts a cross-section of a metal filling processin which the electrically conductive material forms a plurality of viashaving a pillar shape in accordance with one or more embodiments;

FIG. 5A schematically depicts a cross-section of a de-bonding process ofthe glass substrate having a plurality of mushroom-shaped vias inaccordance with the embodiment shown in FIG. 4A;

FIG. 5B schematically depicts a cross-section of a de-bonding process ofthe glass substrate having a plurality of pillar-shaped vias inaccordance with the embodiment shown in FIG. 4B; and

FIG. 5C schematically depicts a cross-section of a de-bonding process ofthe glass substrate having a plurality of pillar-shaped vias inaccordance with the embodiment shown in FIG. 4C.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. Whenever possible,the same reference numerals will be used throughout the drawings torefer to the same or like parts. One embodiment of components used inthe method of the present disclosure is shown in FIG. 1, and isdesignated generally throughout by the reference numeral 100. Thecomponents generally may include a glass substrate including a pluralityof holes bonded to a glass carrier through a bonding layer. The bondinglayer may be etched through the plurality of holes, filled with anelectrically conductive material, and the glass substrate may bede-bonded from the glass carrier.

The methods of the present disclosure enable through-glass vias to bemanufactured in the glass substrate despite challenges associated withhandling of the glass substrate. For example, by bonding the glasssubstrate to a glass carrier, challenges associated with handling a thinglass substrate may be alleviated. In addition, various embodiments mayleverage existing semiconductor processes and process flow whileresulting in more effective metallization.

In the embodiment shown in FIG. 1, the glass substrate 102 including aplurality of holes 104 is bonded to a glass carrier 106 through abonding layer 108. The glass substrate 102 may be used, for example, asan interposer to provide electrical connections within athree-dimensional chip. The glass substrate 102 includes a first face110 and a second face 112 opposite the first face 110. Similarly, theglass carrier 106 includes a first face 114 and a second face 116opposite the first face 114. The glass carrier 106 may enablemanufacturers to reduce a thickness of the glass substrate 102 withoutaltering their existing manufacturing processes or facilities. Aftervias are formed within the glass substrate 102, the glass substrate 102is separated from the glass carrier 106 and the glass carrier 106 may bediscarded or reused in the handling of a subsequent glass substrate. Thefirst face 110 of the glass substrate 102 is separated from the firstface 114 of the glass carrier 106 by a thickness t of the bonding layer108.

The composition and dimensions of the glass substrate 102 are notparticularly limited, and are selected based on the desired end use ofthe glass substrate 102. The glass substrate 102 may be, for example,Eagle XG glass, or Code 2318 glass, manufactured by Corning, Inc. or thelike. Additionally, the glass substrate 102 may be in the shape of awafer having a 4 inch, 6 inch, 8 inch, or 12 inch diameter, for example.Alternatively, the glass substrate 102 may be in the form having anydimensions suitable for its end use. The thickness of the glasssubstrate 102 may also vary depending on its end use. For example, theglass substrate 102 may have a thickness of from about 30 μm to about1000 μm, from about 40 μm to about 500 μm, from about 50 μm to about 200μm, or about 100 μm. In various embodiments, the glass substrate 102 hasa thickness of less than or equal to about 100 μm. In some embodiments,the glass substrate 102 has a thickness of less than 100 μm. It shouldbe understood that a glass substrate of any suitable thickness may beutilized.

The plurality of holes 104 can be formed in the glass substrate 102 byany suitable method. For example, in various embodiments, the pluralityof holes 104 is drilled in the glass substrate 102 using a pulsed laserbeam. The laser beam may be any laser beam having optical propertiescapable of drilling a sacrificial cover layer and the glass substrate102, such as an ultra-violet (UV) laser beam that is a frequency tripledneodymium dopes yttrium orthovanadate (Nd:YVO₄) laser, which emits awavelength of about 355 nm. The laser beam may be pulsed at apredetermined location to form each of the plurality of holes 104 in theglass substrate 102. The plurality of holes may also be mechanicallymachined in some embodiments.

As illustrated in FIG. 1, the glass substrate 102 is bonded to the glasscarrier 106. The glass substrate 102 and the glass carrier 106 may bebonded using a variety of adhesive materials and may or may not beUV-curable adhesives. The bonding layer may be a commercially-availableadhesive from TOK, BS, 3M, or DuPont, including but not limited to, 3MUV-Curable Adhesive LC-3200, 3M UV-Curable Adhesive LC-4200, or 3MUV-Curable Adhesive LC-5200. In various embodiments, an adhesive isapplied to one or both of the first face 110 of the glass substrate 102and the first face 114 of the glass carrier 106. The first face 110 ofthe glass substrate 102 is brought into contact with the first face 114of the glass carrier 106. For example, the adhesive layer can bespin-coated onto one or both of the first face 110 of the glasssubstrate and the first face 114 of the glass carrier 106. Pressureand/or heat may be applied to the glass substrate 102 and the glasscarrier 106 to bond the glass substrate 102 and the glass carrier 106through the bonding layer 108.

In various embodiments, the application of pressure to the glasssubstrate 102 and the glass carrier 106 during bonding causes thebonding layer 108 to extend into at least some of the plurality of holes104, forming an adhesive plug 118. As shown in FIG. 1, the adhesive plug118 extends into the plurality of holes 104 to a height h, as measuredfrom the first face 110 of the glass substrate 102 to a distal face 120of the adhesive plug 118. Accordingly, the bonding layer 108 may have athickness t between the first face 110 of the glass substrate and thefirst face 114 of the glass carrier 106, and a thickness of t plus hinside the plurality of holes 104, as measured from the distal face 120of the adhesive plug 118 to the first face 114 of the glass carrier 106.

After the glass substrate 102 is bonded to the glass carrier 106, anetch-back process is employed to remove the adhesive plug 118. Removalof the adhesive plug 118 from within the plurality of holes 104 servesto further shape the plurality of holes 104 by removing resin and glassfibers so that when the plurality of holes is filled with electricallyconductive material, the electrically conductive material can smoothlyand completely coat the interior of the holes, thus forming an effectiveconnection between layers on either side of the glass substrate.

As shown in FIG. 2, an etchant 200 is introduced through the pluralityof holes 104 at the second face 112 of the glass substrate 102. Theetching process is not particularly limited and can include wet etchingprocesses or dry etching processes.

In various embodiments, a wet etch process is employed to etch back thebonding layer 108. In such embodiments, the etchant 200 may be anetching solvent. The bonding layer 108 can be exposed to the etchingsolvent through the plurality of holes 104. The glass substrate 102functions as a hard mask for the etching process. For example, eachadhesive plug 118 and portions of the bonding layer 108 extending fromthe adhesive plug 118 to the first face 114 of the glass carrier 106 maybe exposed to the etchant 200, while portions of the bonding layer 108between the first face 110 of the glass substrate 102 and the first face114 of the glass carrier 106 where there is no hole may not be exposedto the etchant 200. Accordingly, the portions of the bonding layer 108that extend into the plurality of holes 104 (making up the adhesiveplugs 118) and between the adhesive plugs 118 and the first face 114 ofthe glass carrier 106 may be etched away while the other portions of thebonding layer 108 remain.

The etching solvent may include, but is not limited to, at least one ofhydrofluoric acid, ammonium fluoride, nitric acid, acetic acid, acetone,or combinations thereof. In various embodiments, the etching solvent caninclude buffered oxide etch (i.e., BOE, buffered HF, or BHF) or acetone.Other etching solvents may be employed, depending on the particularadhesive material in the bonding layer and the particular glasscomposition of the glass substrate 102 and the glass carrier 106. Inparticular, suitable etching solvents have high selectivity between thebonding layer 108 and the glass of the glass substrate 102 and the glasscarrier 106. The etching solvent may be sprayed on to the glasssubstrate 102 or the components 100 may be immersed in the etchingsolvent.

In other embodiments, a dry etch process is employed to etch back thebonding layer 108. In such embodiments, a plasma etcher may be utilizedto etch back the bonding layer 108 using a plasma generated from an O₂or Argon-containing gas. Other dry etching processes may be employed.The dry etch process may be controlled by time or it can be stopped whenthe etching reaches the glass carrier 106.

Whether the etching is performed using a wet etch process or a dry etchprocess, the bonding layer 108 inside the plurality of holes 104 isetched back through the distal face 120 of the adhesive plugs 118 suchthat the adhesive plugs 118 are removed, as shown in FIG. 2. Theduration of the etching process is not limited and may be determinedbased on the etch rate and the desired depth of etch back.

As shown in FIGS. 3A-3C, in various embodiments, the bonding layer 108is etched backed to a depth d through the plurality of holes 104. Asused herein, the depth d represents the depth into the bonding layer 108measured from the distal face 120 of the adhesive plug 118 (e.g., thesum of the depth h plus at least a portion of the thickness t). Forexample, when the etch back process is used to etch back only theadhesive making up the adhesive plugs 118 and does not etch adhesivematerial of the bonding layer 108 past the first face 110 of the glasssubstrate 102, the depth d is equal to the height h of the adhesive plug118, as shown in FIG. 3A. In some embodiments, such as where the bondinglayer 108 does not extend into the plurality of holes 104, the depth dis less than or equal to the thickness t of the bonding layer 108, asshown in FIG. 3B. When the etch back process is used to etch back theadhesive plugs 118 and further etches at least partially through thethickness t of the bonding layer 108, the depth d is equal to the sum ofthe height h plus the portion of the thickness t, as shown in FIG. 3C.In various embodiments, the length l represents the length into thebonding layer 108 the etching extends, as measured from the first face110 of the glass substrate 102. For example, in FIG. 3B, the length l isequal to the depth d, because there was no adhesive plug (e.g., theheight h is equal to zero). In FIG. 3C, the length l is equal to thedifference between the depth d and the height h. Accordingly, the depthd is equal to the sum of the height h of the adhesive plug, if any, andthe length l.

Once the etching process is complete, the plurality of holes 104 isfilled with an electrically conductive material. The electricallyconductive material may be, by way of example and not limitation,copper, silver, aluminum, nickel, alloys thereof, and combinationsthereof. In some embodiments, the plurality of holes 104 is filled witha copper-containing material, such as a copper alloy.

The filling process may be any suitable metal filling process, includingbut not limited to, a wave soldering process, physically placing asolder paste into the plurality of holes, a vacuum solder technique, orany other metal filling technique known or used in the art. In someembodiments, a physical vapor deposition (PVD, or sputtering) orchemical vapor deposition process may be used to coat the interior wallsof the plurality of holes 104 with electrically conductive material toform an electrically conductive layer prior to filling the plurality ofholes 104 with the electrically conductive material. In otherembodiments, deposition of the electrically conductive layer may includean electroless or electrolytic plating process. In such embodiments, aseed layer may be formed on the interior walls of the plurality of holes104 before the electrically conductive material is plated. For example,a seed layer may be deposited, followed by a copper deposition processto form an electrically conductive layer on the interior walls of theplurality of holes 104. Although some filling processes may includeformation of an electrically conductive layer prior to filling theplurality of holes 104, formation of the electrically conductive layermay not be necessary in some embodiments. For example, when vacuummethods are employed to fill the plurality of holes 104, plating of anelectrically conductive layer may be eliminated.

FIGS. 4A-4C schematically depict a cross-section of a process of fillingthe plurality of holes 104 with an electrically conductive material.When the plurality of holes 104 are filled with the electricallyconductive material, the electrically conductive material may completelyfill the portion of the bonding layer 108 that was etched back and theplurality of holes 104. At least a portion of the electricallyconductive material may protrude from the first face 110 of the glasssubstrate 102, extending into the bonding layer 108 to the length l toform a plurality of vias 400 in the glass substrate 102. As shown inFIG. 4A, in some embodiments, such as when a wet-etch process is used,the electrically conductive material may fill a mushroom-shaped voidcreated by the etching process such that the vias 400 include a portionof the electrically conductive material that protrudes from the firstface 110 of the glass substrate 102.

In other embodiments, such as the embodiment depicted in FIGS. 4B and4C, the etching process may form a one directional void. For example,when a dry-etch process is employed, the bonding layer may only beetched in a single direction such that the void will not expandlaterally beyond the first face 110 of the glass substrate 102.Accordingly, the electrically conductive material may form apillar-shaped void, resulting in a pillar-shaped via 400, as shown inFIGS. 4B and 4C. In other words, the via 400 may have the shape of acylinder having substantially parallel sides that extend from the firstface 110 of the glass substrate 102 in a direction that is substantiallyperpendicular with the first face 110 of the glass substrate 102. Inembodiments in which the dry-etch process utilizes the first face 114 ofthe glass carrier 106 as a stop layer, the bonding layer 108 is etchedto a length l that is equal to the thickness t of the bonding layer 108and the pillar-shaped via 400 may extend from the first face 100 of theglass substrate 102 the length l, as shown in FIG. 4B. When the dry-etchprocess is controlled by time, the bonding layer 108 may be etched backto a length l into the bonding layer 108, where the length l is lessthan the thickness t of the bonding layer 108, and the pillar-shaped via400 may extend from the first face 100 of the glass substrate 102 thelength l, as shown in FIG. 4C.

Once the plurality of holes 104 are filled with the electricallyconductive material 400, the glass substrate 102 may be de-bonded fromthe bonding layer 108 and the glass carrier 106, as shown in FIGS.5A-5C. De-bonding may be performed using any suitable process. Forexample, in embodiments in which the bonding layer 108 comprises aUV-cured adhesive, a laser may be used to destroy the bonds between theadhesive and the glass substrate 102. Other laser and baking methods maybe employed to separate the bonding layer 108 from the glass substrate102. Alternatively or in addition, dicing tape may be applied to theglass substrate 102 during the de-bonding process prior to using a laserto de-bond the glass substrate 102 from the glass carrier 106. In someembodiments, the glass carrier 106 may first be de-bonded from thebonding layer 108, and then the bonding layer 108 may be removed fromthe glass substrate 102 including the plurality of vias 400.

In various embodiments, the de-bonding process leaves substantially noadhesive residue on the glass substrate 102 including the plurality ofvias 400. For example, the de-bonding process may include a step inwhich de-taping tape (available from 3M) is used to peel the adhesivefrom the first face 110 of the glass substrate 102.

FIG. 5A illustrates the embodiment of FIG. 4A during the de-bondingprocess. In particular, the plurality of vias 400 protrude from thefirst face 110 of the glass substrate 102 when the glass substrate 102is de-bonded. In embodiments in which the bonding layer 108 was etchedto the length l, the electrically conductive material protrudes from thefirst face 110 of the glass substrate 102 the length l. Similarly, FIG.5B and FIG. 5C illustrate the embodiments of FIG. 4B and FIG. 4C,respectively, during the de-bonding process. In FIGS. 5B and 5C, theplurality of vias 400 are pillar shaped, and extend from the first face100 of the glass substrate 102. In embodiments in which the bondinglayer 108 was etched to the length l into the bonding layer 108, thepillars extend from the first face 110 of the glass substrate 102 thelength l. For example, in FIG. 5B, the length l is equal to thethickness t of the bonding layer. In FIG. 5C, the length l is less thanthe thickness t of the bonding layer.

It should now be understood that embodiments of the present disclosureenable through-glass vias to be formed in a thin glass substrate whileleveraging the existing manufacturing processes in the semiconductorindustry. In particular, various embodiments enable the glass substrateto be removably coupled to a glass carrier for handling. In variousembodiments, the etching back of the bonding layer further leverages theglass substrate and the glass carrier to simplify the etching process byreducing or even eliminating the need for an additional mask and/or stoplayer.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

1-20. (canceled)
 21. An assembly comprising: a substrate having a firstface and a second face; a carrier; a bonding layer positioned betweenthe first face of the substrate and a face of the carrier to bond thesubstrate and carrier; a plurality of vias extending through thesubstrate from the first face of the substrate to the second face of thesubstrate and into at least a portion of the bonding layer.
 22. Theassembly of claim 21, wherein the bonding layer is capable of beingde-bonded from the substrate.
 23. The assembly of claim 22, wherein thebonding layer is an ultraviolet curable adhesive.
 24. The assembly ofclaim 21, wherein the vias are filled with an electrically conductivematerial.
 25. The assembly of claim 24, wherein the electricallyconductive material is selected from a group consisting of copper,silver, aluminum, nickel, alloys thereof, and combinations thereof. 26.The assembly of claim 24, wherein the electrically conductive materialcomprises copper-containing material.
 27. The assembly of claim 21,wherein the plurality of vias extend through an entire thickness of thebonding layer.
 28. The assembly of claim 21, wherein the plurality ofvias extend through less than an entire thickness of the bonding layer.29. The assembly of claim 21, wherein the substrate is glass.
 30. Theassembly of claim 21, wherein the carrier is glass.
 31. The assembly ofclaim 21, wherein each of the plurality of vias is pillar-shaped. 32.The assembly of claim 21, wherein each of the plurality of vias ismushroom-shaped.
 33. The assembly of claim 21, wherein the substrate hasa thickness of less than or equal to 100 um.